Wang Yumeng, Hu Mingxia, Yue Qianqian, Xiaoqing Feng, Zhao Yanying
School of Chemistry and Chemical Engineering, School of Materials Science and Engineering, Zhejiang Sci-Tech University Hangzhou 310018 China
School of Pharmacy, School of Medicine, Changzhou University Changzhou 213164 China
RSC Adv. 2024 Dec 17;14(53):39759-39768. doi: 10.1039/d4ra06147k. eCollection 2024 Dec 10.
Although multicolor luminescent materials are widely used in information encryption and decryption based on the excited-state intramolecular proton transfer (ESIPT) reaction, there remains a significant gap in the mechanistic understanding of how solvent and pH conditions influence the ESIPT process. Owing to their ability to avoid self-absorption as well as provide large Stokes' shift and strong emission properties, ESIPT-generated molecules (ESIPT gens) have recently emerged as highly potential fluorophores. Herein, the ESIPT mechanism of bromine-based (2'-hydroxy-5'-bromo)phenylbenzimidazole (HBI-pBr) was investigated in solvents using spectroscopic measurements and time-dependent density functional theory (TD-DFT) calculations. The results indicated that multi-color fluorescence emissions were observed at 470, 458 and 416 nm in CHOH doped with a base and acid. The potential energy profile rationalized the fluorescence mechanistic insights into the ESIPT reaction and pH-dependent dual response. Notably, nucleus-independent chemical shift (NICS_ZZ) values were applied to reveal the ESIPT process. We leveraged the bromine atom as an electron withdrawing group to manipulate ground and excited-state proton transfer, thereby offering a strategic approach for designing and developing an ESIPT fluorescence sensor for the detection of H and OH. By studying the effect of solvent and pH conditions on HBI-pBr, the multicolor fluorescence mechanism of ESIPT was elucidated, thus laying a solid foundation for the design and synthesis of luminescent materials based on the ESIPT reaction.
尽管多色发光材料基于激发态分子内质子转移（ESIPT）反应在信息加密和解密中得到广泛应用，但在溶剂和pH条件如何影响ESIPT过程的机理理解方面仍存在显著差距。由于能够避免自吸收以及提供大的斯托克斯位移和强发射特性，ESIPT产生的分子（ESIPT gens）最近已成为极具潜力的荧光团。在此，使用光谱测量和含时密度泛函理论（TD-DFT）计算在溶剂中研究了溴基（2'-羟基-5'-溴）苯基苯并咪唑（HBI-pBr）的ESIPT机理。结果表明，在掺杂有碱和酸的CHOH中，在470、458和416 nm处观察到多色荧光发射。势能剖面图阐明了对ESIPT反应和pH依赖性双重响应的荧光机理见解。值得注意的是，应用了非核独立化学位移（NICS_ZZ）值来揭示ESIPT过程。我们利用溴原子作为吸电子基团来操纵基态和激发态质子转移，从而为设计和开发用于检测H和OH的ESIPT荧光传感器提供了一种策略性方法。通过研究溶剂和pH条件对HBI-pBr的影响，阐明了ESIPT的多色荧光机理，从而为基于ESIPT反应的发光材料的设计和合成奠定了坚实基础。
